1.\" 2.\" $Id$ 3.\" 4.Dd Sep 28, 1998 5.Dt BRIDGE 4 6.Os 7.Sh NAME 8.Nm bridge 9.Nd Bridging support 10.Sh DESCRIPTION 11Starting from version 2.2.8, FreeBSD supports bridging on ethernet-type 12interfaces. This is achieved using the following option 13.Bd -literal 14 options BRIDGE 15.Ed 16 17in the kernel config file, and is controlled by two 18.Nm sysctl 19variables: 20.Bd -literal 21 net.link.ether.bridge 22.Ed 23 24Set to 1 to enable bridging, set to 0 to disable it 25.Bd -literal 26 net.link.ether.bridge_ipfw 27.Ed 28 29Set to 1 to enable 30.Nm ipfw 31filtering on bridged packets. Note that 32.Nm ipfw 33rules only apply 34to IP packets. Non-IP packets are subject to the default 35.Nm ipfw 36rule (number 65535) which must be an 37.Ar allow 38rule if we want ARP and other non-IP packets to flow through the 39bridge. 40 41 42.Sh BUGS 43.Pp 44Care must be taken not to construct loops in the bridge topology. 45The kernel supports only a primitive form of loop detection, by disabling 46some interfaces when a loop is detected. No support for a daemon running the 47spanning tree algorithm is currently provided. 48.Pp 49With bridging active, interfaces are in promiscuous mode, 50thus causing some load on the system to receive and filter 51out undesired traffic. 52.Pp 53Extended functionality to enable bridging selectively on clusters 54of interfaces is still in the works. 55.Pp 56Not all interface support bridging -- at the moment it works for 57``ed'', ``de'', ``ep'', ``fxp'', ``lnc'' interfaces. 58.Sh SEE ALSO 59.Xr ip 4 , 60.Xr ipfw 8 , 61.Xr sysctl 8 . 62.Sh HISTORY 63.Nm 64bridging has been introduced in FreeBSD 2.2.8 65by Luigi Rizzo <luigi@iet.unipi.it>. 66